In many searching or browsing applications, users interact with collections of images, videos, or other content through thumbnail images which communicate to the user the type of content that the user will find upon clicking the thumbnail.
In some instances, a thumbnail might be created by simply resizing a rectangular source image, while maintaining the existing aspect ratio between the height and width of the image. In other instances that occur frequently, the dimensions of the thumbnail are constrained to be a fixed aspect ratio which is different from the aspect ratio of the source image.
Generating the latter type of thumbnail often involves cropping the image so that some of the original content will be omitted. If this crop is not performed carefully, important content (such as a person's face or key text) might be absent from the thumbnail, obscuring the meaning of the original image.
Human editors can perform this cropping, at a cost in terms of both time and expense. To minimize this cost, cropping through automated processes might be used, in a trade-off that tends to result in a thumbnail of lower quality.